1. Field of the Invention
The present invention relates to a technical field of a signal delay apparatus, a leakage signal removing apparatus and an information processing apparatus. More specifically, the present invention relates to a technical field of a signal delay apparatus for controlling delay amounts of detected signals, which are obtained from a plurality of tracks formed on a recording medium, respectively, a leakage signal removing apparatus including the forgoing signal delay apparatus for removing a leakage signal caused by the detected signals of other trucks from any detected signal and an information processing apparatus including the foregoing leakage signal removing apparatus.
2. Description of the Related Art
Conventionally, in the case that the information is detected from the truck formed on the recording medium such as an optical disk or the like, an optical beam is irradiated to this truck and this information is detected on the basis of the reflected light of this optical beam from the track.
On one hand, in recent years, narrowing of truck pitch (namely, narrowing of spacing between the trucks, which are adjacently formed) in the trucks on the recording medium is noticeable at the request of improvement of the recording density. However, in this case, if the optical beam is irradiated to the truck, in which the information to be detected is recorded, a portion of a light spot formed by that optical beam on the recording medium is also irradiated on the truck adjoining the truck to be irradiated (namely, the truck which should not be originally irradiated by the optical beam). As a result, there was a case such that the information recorded in that adjoining truck was leaked in its reflection light as so-called cross talk (a leakage signal).
Therefore, conventionally, the above optical beam is divided into three on a flat surface by using a diffraction grating or the like. Then, a central one of them (hereinafter, referred to as a main beam) is irradiated toward the truck to be originally irradiated and other two beams (hereinafter, referred to as a sub beam, respectively) are irradiated to the two trucks adjoining the both sides of the truck to be originally irradiated, respectively. After that, two detected signals to be obtained from the reflection light of the sub beam are subtracted from the detected signals obtained from the reflection light of the main beam, so that the above described cross talk component, which is included in the detected signal obtained from the reflection light of the main beam, is deleted.
In the above case, according to the conventional cross talk deleting system, the main beam and two sub beams are generated by the diffraction grating or the like, so that a line connecting an irradiation center point of respective beams on the recording medium was not orthogonal to a moving direction of respective trucks.
Therefore, according to the conventional leakage signal removing system, the detected signals obtained from the reflection light of one of the sub beams and the detected signals obtained from the reflection light of the main beam are delayed by fixed times, which are different each other. Then, after orthogonalizing the line connecting the irradiation center points of respective beams and the moving direction of respective trucks for processing the signals (i.e., apparently), the two detected signals obtained from the reflection light of the sub beam are subtracted from the detected signals obtained from the reflection light of the main beam, respectively, so as to remove the above described cross talk.
However, according to the above described tendency of narrowing of truck pitch, the spacing between the above main beam and respective sub beams is also apt to be narrowed. Therefore, it is necessary to fix the spacing more exactly and remove the cross talk. On the contrary, if the oscillation wavelength of the semiconductor laser serving as an ejection source of respective optical beams is changed, the separation condition by the diffraction grating is changed. As a result, the spacing between the main beam and the sub beams subjects to be changed.
In this case, if this spacing is changed, originally, it is necessary to change the delay amount of respective detected signals depending on the change of the spacing. However, as described above, conventionally, the delay amount is always fixed for respective detected signals, so that this involves a problem such that it is not possible to obtain an appropriate delay amount for orthogonalizing the line connecting the irradiation center point of respective beams and the moving direction of respective trucks for processing the signals in response to the oscillation wavelength of the optical beam.
Further, this problem leads to a problem such that it is not possible to appropriately remove the cross talk and the detected signal is generated as the noise by the cross talk remains in the detected signal in association with the information to be detected, so that the information by the use of this detected signal can not be accurately recorded or reproduced.
The present invention has been made taking the present problems into consideration, an object of which is to provide a signal delay apparatus capable of calculating an accurate signal delay amount for removing the cross talk even in the case that the irradiation manner of the optical beam such as the beam spacing or the like is changed, a leakage signal removing apparatus capable of more accurately removing the cross talk and further, an information processing apparatus capable of accurately performing the information processing such as recording or playing or the like by the use of the detected signal, from which the cross talk is accurately removed.
The above object of the present invention can be achieved by a signal delay apparatus of the present invention for delaying any one of detected signals, which are optically obtained from a plurality of adjoining trucks. The apparatus is provided with: an extracting device for extracting a specific main detected signal having a predetermined specific waveform from a main detected signal which is obtained from a main truck among said trucks; a holding device for holding a sub detected signal which is obtained from a sub truck when said specific main detected signal is extracted; an averaging device for averaging a plurality of said sub detected signals, which are held by said holding device during a predetermined time frame, and generating an averaged detected signal; a calculating device for comparing a waveform of said generated averaged detected signal with said specific waveform and calculating the delay amount for any one of said detected signals; and a delay device for delaying at least any one of said detected signals by said calculated delay amount.
According to the present invention, the delay amount of at least any one of detected signals is calculated by comparing a waveform of an obtained averaged detected signal and a specific waveform, so that, even if the irradiation manner of the optical beam to be irradiated to respective trucks is changed, it is possible to delay respective detected signals by accurately calculating the delay amount.
In one aspect of the present invention, said specific waveform comprises a zero cross waveform.
According to this aspect, the delay amount is calculated by using a zero cross waveform as a typical specific waveform, so that it is possible to simply and accurately calculate the present delay amount.
In another aspect of the present invention, said specific waveform is provided with a waveform of said main detected signal, which is obtained from any one of a pit formed on said main truck in association with said information and a gap between pits, having a length which is longer than the length obtained by multiplying a unit length of at least any one of said pit and gap by a predetermined number.
According to this aspect, a waveform of the main detected signal, which is obtained from a pit or spacing between pits having a length not less than a predetermined length, is defined as a specific waveform, so that it is possible to enlarge a capture range in the delay amount control and calculate the present delay amount accurately.
In further aspect of the present invention, said specific waveform during a predetermined time from said detected signal is started to be obtained is provided with a waveform of said main detected signal, which is obtained from any one of a pit formed on said main truck in association with said information and a gap between pits, having a length which is longer than the length obtained by multiplying a unit length of at least any one of said pit and gap by a predetermined number, and said specific waveform after said time passed over is provided with a waveform of said main detected signal, which is obtained from any one of said pit and gap having all lengths.
According to this aspect, just after the present detected signal is started to be obtained and the detected signal becomes unstable, a waveform of the main detected signal, which is obtained from a pit or spacing between pits having a length not less than a predetermined length, is defined as a specific waveform and then, the delay amount is calculated as the waveform of the main detected signal, which is obtained from all pits or spacing between pits, is defined as a specific waveform, so that it is possible to calculate the present delay amount more accurately.
In further aspect of the present invention, said predetermined number is provided with a number corresponding to a length, which is longer than the shortest length of any one of said pit and gap, from which said main detected signal is obtained.
According to the present invention, the delay amount is calculated by using the detected signal, which is obtained under a wide captain challenge, as well as a good ratio between a signal and noise is provided, so that it is possible to calculate the present delay amount more accurately.
In further aspect of the present invention, said delay device is provided with a shift register.
According to this aspect, it is possible to simply realize a delay device.
In further aspect of the present invention, said delay device is provided with a shift register and a FIR (Finite Impulse Response) filter.
Accordingly, it is possible to delay the detected signal more accurately.
In further aspect of the present invention, said FIR filter comprises two taps and a sum of respective tap coefficients in association with said respective taps is 1.
According to this aspect, it is possible to realize the delay device by using a simple FIR filter.
In further aspect of the present invention, said sub truck is provided with said two trucks, which are adjacently formed on the opposite sides of said main truck and an irradiation position of respective optical beams, which are irradiated to said sub truck, moves to said main truck side rather than said respective sub trucks, so that said respective optical beams are irradiated.
According to this aspect, on the basis of a sub detected signal, which is obtained by a higher ratio between a signal and noise, it is possible to calculate the delay amount more accurately.
In further aspect of the present invention, said main truck comprises said truck, in which said information to be read is recorded.
According to this aspect, it is possible to calculate the delay amount so that the information is capable of being read more accurately.
In further aspect of the present invention, said main truck comprises said truck, which adjoins to said truck, in which said information to be read is recorded.
According to this aspect, it is possible to calculate the delay amount so that the information is capable of being read more accurately.
The above object of the present invention can be achieved by a leakage signal removing apparatus of the present invention. The apparatus is provided with: (i) a signal delay apparatus for delaying any one of detected signals, which are optically obtained from a plurality of adjoining trucks, is provided with: an extracting device for extracting a specific main detected signal having a predetermined specific waveform from a main detected signal which is obtained from a main truck among said trucks; a holding device for holding a sub detected signal which is obtained from a sub truck when said specific main detected signal is extracted; an averaging device for averaging a plurality of said sub detected signals, which are held by said holding device during a predetermined time frame, and generating an averaged detected signal; a calculating device for comparing a waveform of said generated averaged detected signal with said specific waveform and calculating the delay amount for any one of said detected signals; and a delay device for delaying at least any one of said detected signals by said calculated delay amount, (ii) a removing device for removing a leakage signal, which is mixed in said main detected signal, from said detected signal, which is obtained from said sub truck by using said detected signal, which is obtained from said sub truck and is delayed by said delay device.
According to the present invention, it is possible to remove a leakage signal (cross talk) in the main detected signal more accurately.
The above object of the present invention can be achieved by a signal processing apparatus is provided with: (a) a leakage signal removing apparatus is provided with (i) a signal delay apparatus for delaying any one of detected signals, which are optically obtained from a plurality of adjoining trucks, comprising: an extracting device for extracting a specific main detected signal having a predetermined specific waveform from a main detected signal which is obtained from a main truck among said trucks; a holding device for holding a sub detected signal which is obtained from a sub truck when said specific main detected signal is extracted; an averaging device for averaging a plurality of said sub detected signals, which are held by said holding device during a predetermined time frame, and generating an averaged detected signal; a calculating device for comparing a waveform of said generated averaged detected signal with said specific waveform and calculating the delay amount for any one of said detected signals; and a delay device for delaying at least any one of said detected signals by said calculated delay amount, (ii) a removing device for removing a leakage signal, which is mixed in said main detected signal, from said detected signal, which is obtained from said sub truck by using said detected signal, which is obtained from said sub truck and is delayed by said delay device, (b) a processing device for effecting at least any one of recording of said information in said truck or playing of said information on the basis of said main detected signal, of which said leakage signal is removed.
According to the present invention, it is possible to accurately perform any one of recording or playing by the use of the main detected signals, from which the leakage signals are accurately removed.